Electrical switch having a movable contact rolling between stationary contacts

ABSTRACT

A round movable contact is moved into engagement with a pair of stationary contacts such that the movable contact will seat between the stationary contacts and upon continued cycling of the switch the movable contact will tend to deform faces of the stationary contact to provide a self-cleaning contact surface on the movable contact and provide a new seat in the stationary contact as it progresses therethrough.

United States Patent Utken et a1.

1 1 Dec. 16, 1975 1 1 ELECTRICAL SWITCH HAVING A 2,935,585 5/1960Holcombe 200/166 BB x MOVABLE CONTACT ROLLING BETWEEN 3,001,046 9/1961Racz et a1. 200/166 BB X 3,032,620 5/1962 Siiberg 200/166 BB XSTATIONARY CONTACTS 3,311,717 3/1967 Lace 200/166 BB X [75] Inventors:Jay Utken; Edgar F. Hauenstine,

both of Frankfort, 1nd. Primary ExaminerRobert K. Schaefer [73]Assigneez p. Mallory & hm Assistant ExaminerWi1liam J. SmithIndianapolis Ind Attorney, Agent, or FirmChar1es W. Hoffmann; Robert F.Meyer; Dona1d W. Hanson [22] F11ed: Feb. 1, 1973 r [21] Appl. No.:328,869 [57] ABSTRACT A round movable contact is moved into engagement152 US. Cl 200/277; 200/155 R; 200/288 with a p Of Stationary ContactsSuch that the [51] Int. Cl. H01h 1/16 able Contact will Seat between theStationary Contacts [58] Field of Search 200/166 BB, 277; 338/157 andupon continued cycling of the switch the movable 333/158 contact willtend to deform faces of the stationary contact to provide ase1f-cleaning contact surface on [56] References Cit d the movablecontact and provide a new seat in the sta- UNITED STATES PATENTS tionarycontact as it progresses therethrough.

1,520,847 12/1924 Bartholomew 7. 200/166 BB 6 Claims, 4 Drawing FiguresUS. Patent Dec. 16, 1975 3,927,288

ELECTRICAL SWlTCI-I HAVING A MOVABLE CONTACT ROLLING BETWEEN STATIONARYCONTACTS This invention relates to electrical switches and morespecifically to the type of switches which are accompanied with a snapaction mechanism. More particularly, the present invention relates toelectrical switches wherein a self-centering movable contact engages apair of stationary contacts.

Aside from mechanical failure or breakage of such a switch mechanism,its switch life is heavily dependent upon electrical contact life, ormore specifically, the life of the contact surfaces which engage oneanother. For example, with repeated cycling, high inrushes of current,in combination with contact bounce, causes spurious arcing and thecontact surfaces are degraded to the point where the switch is no longerfunctional. Further, severe arcing can result in an early failure of theswitch due to the arc jumping to other elements of the switch.

Accordingly, the present invention is concerned with an electricalswitch wherein a movable contact engages a pair of stationary contactsand has as one of its objects the provision of a switch having longercontact life.

Another object of the invention is the provision of a switch whichprovides a nesting action between fixed and movable contacts tosubstantially eliminate contact bounce.

It is another object of the present invention to provide a pair ofstationary contacts positioned in substantially the same plane as thedirection of movement of a movable round contact.

Another object of the present invention is to provide an electricalswitch with at least a pair of stationary contacts positioned in thepath of a movable contact such that the movable contact will roll andengage one of the stationary contacts prior to engaging the secondstationary contact.

Yet another object of the present invention is to provide an electricalswitch such that a movable contact will engage a pair of stationarycontacts in a way to nest the movable contact between the stationarycontacts.

Still another object of the present invention is to confine the travelof a round movable contact to an operating area bordered by at least twostationary contacts.

These and other objects will become more apparent from the followingdescription and accompanying drawing wherein:

FIG. 1 is a side elevation of an electrical switch coupled to a volumecontrol with portions broken away for purposes of clarity;

FIG. 2 is a cross-section taken along lines 22 of FIG. 1 and showing theswitch in one position of operation;

FIG. 3 is a view similar to FIG. 2 but showing the switch in a secondposition of operation; and

FIG. 4 is an enlarged view of stationary contacts and movable contactsof the switch after repeated cycling in accordance with the invention.

Generally speaking the objects of the invention are accomplished byproviding an electrical switch having a self-centering round movablecontact engaging at least a pair of stationary contacts by rolling theround 2 movable contact along one of the stationary contacts with thepair of stationary contacts disposed in spaced angular relationship toeach other such that continued rolling of the movable contact causes itto nest between the pair of stationary contacts.

Referring now to the drawings and more specifically to FIGS. 1-3 anelectrical switch 10 is illustrated as being attached to a volumecontrol 12. As will become apparent, electrical switch 10 is of a snapacting type switch wherein a movable contact is self-centering due toits movement being initiated through a one point contact. Although theconcepts of the invention are not limited thereto, the particular switchillustrated as having a self-centering feature is more particularlydescribed in US. Pat. No. 2,820,864 issued Jan. 21, 1958 to W. K.Newman, et al. Volume control 12 includes a shaft 14 rotationallycoupled to a rotor 16 for the purpose of changing a variable resistance(not shown) in the control 12. Rotor 16 is provided with a boss 18 tofacilitate actuation of electrical switch 10. In the illustrativeembodiment, switch 10 is of the single-pole double-throw type and isprovided with a snap actuation means 11. Snap-action means 11 includes arotatable actuator 22, provided with a pair of legs 20 extending intocontrol 12, spring 30, and a switch actuator blade 28. Boss 18 may berotated into an interference path with one of the legs 20 to change theposition of rotatable actuator 22. Rotatable actuator 22 is positionedin a switch housing 24 and supported in the housing to pivot about pivotpost 26. Switch actuator blade 28 is also supported for rotationalmovement in the housing 24 about post 26. Spring 30 is connected betweenrotatable actuator 22 and switch actuator blade 28. Rotation of legs 20through rotor 16 and boss 18 will cause rotation of rotatable actuator22 in the direction of arrow 22' to compress spring 30 to move one ofits ends through an overcenter condition. Spring 30 will thereby bereleased and impart motion to switch actuator blade 28 in the directionof arrow 28' to rotate it to the position shown in FIG. 3.

Located near the center of switch actuator blade 28 and extending upwardfrom its face 32 is a boss 34 which is provided with a rib 36 extendingacross its diameter. A movable contact means 38 is provided by a contactring 40 which floats around boss 34 and is disposed between switchactuator blade 28 and terminal board 42. The cooperation of rib 36 withring contact 40 provides the self-centering characteristics of the ringcontact.

As shown in FIG. 1, a switch housing 24 is closed at one end by aninsulative terminal board 42. Insulative terminal board 42 is retainedin place by a plurality of tabs 44 which are crimped over the outer facethereof. To provide electrical continuity from the inside of the switch10 to external circuitry, a plurality of terminals are staked intoterminal board 42. Terminal means 46 includes a common terminal 48,having a stationary contact portion 50 located inside housing 24, andterminals 52 and 56 with their stationary contacts 54 and 58,respectively, also extending into switch housing 24.

As illustrated in FIGS. 2 and 3 it may be seen that the geometricallocation of terminals 48, 52 and 56, with their stationary contacts 50,54 and 58, respectively, are positioned in such a manner that ringcontact may be moved from a first position, as illustrated In FIG. 2, toa second position as shown in FIG. 3. A shown, stationary contacts 54and 58 are rectangular III shape and are in tandem relation with a space57 ther= between, and they are also slightly skewed with respect to eachother. Stationary contact 50 which is also rectangular is spaced fromthe two contacts which are in tandem and is substantially in line withspace 57. Ring contact 40 is limited in its travel to an area boarderedby stationary contacts 50, 54 and 58. As switch actuator blade 28 movesring contact 40, by way of rib 36, ring contact 40 rolls along thecommon stationary contact 50. A sufficient amount of clearance isprovided with the present arrangement of the stationary contacts suchthat a relatively small amount of movement is required by the switchactuator blade 28 to move ring contact 40 from one position to theother.

Since ring contact 40 is moved through a one point contact of the rib 36so as to be self-centering, it may find its own seat between stationarycontacts 50 and 54 as seen in FIGS. 2 and 3. More specifically,stationary contacts 50 and 54 are positioned a distance apart from eachother sufficient to provide a nesting between the ring and stationarycontacts when ring contact 40 is placed between either one of the two.As switch actuator blades 28 moves from the position shown in FIG. 2 tothat of FIG. 3, ring contact 40 will remain nested between commonstationary contacts 50 and stationary contact 54 to assure thatelectrical continuity is continued until the rib 36 of the switchactuator blade 28 moves across the central opening 41 of contact ring40. When rib 36 imparts motion to the ring contact 40 on the oppositeside of the ring, contact ring 40 will, as shown in FIG. 3, be nestedbetween stationary contacts 50 and 58.

The operation of the switch may now be described. Shaft 14 of volumecontrol 12 may be manually rotated so that boss 18 on rotor 16 willimpart motion to rotatable actuator 22 of switch by way of legs 20. Asrotatable actuator 22 is displaced from a position shown in FIG. 2 tothat shown in FIG. 3, compression spring 30 is compressed untilrotatable actuator 22 moves it through an over-center condition to allowthe spring to be released to displace switch actuator blade 28. Whenswitch actuator blade 28 is displaced from a position as shown in FIG. 2to that shown in FIG. 3, rib 36 on boss 34 will impart motion to ringcontact 40 to move it to a position shown in FIG. 3. As ring contact 40comes into engagement with stationary contacts 50 and 58, the one pointcontact of the rib 36 will allow the ring contact 40 to find its ownseat between the contacts. Rotation of shaft 14 in the oppositedirection will, in like manner, return contact 40 to the position shownin FIG. 2.

Ring contact 40 will tend to move differently depending upon theposition in which the switch is mounted. Should switch 10 be mounted ina position as viewed in FIGS. 2 and 3, ring contact 40 will tend to dropbetween the stationary contacts 54 and 58 as it travels from theposition shown in FIG. 2 to that shown in FIG. 3. In this particularpath of movement, ring contact 40 will make contact with stationarycontact 58 prior to seating between stationary contacts 50 and 58 byrotating into engagement with stationary contact 50. Should switch 10 bemounted in a position inverted from that of FIGS. 2 and 3, ring contact40, due to gravity, will tend to roll along the common stationarycontact 50 to therefore be in contact with stationary contact 50 priorto engagement with stationary contact 58. Ring contact 40 will tend toroll into engagement with stationary contact 58 to become lodged betweenstationary contacts 50 and 58. In either event the movable contact willbe seated between cooperating stationary contacts.

The contact engagement characteristics of ring contact 40 and stationarycontact 50 and 58 will also apply with respect to stationary contacts 50and 54 in substantially the same manner. Upon repeated cycling of theswitch 10, the continual impacting of the ring 40 into engagement withthe contacts 50, 58 and 50, 54 will cause the material of the stationarycontacts to be displaced. Stationary contacts 50 and 58 have beenarranged to allow for contact surface displacement such that changing ofthe relative relationship between the movable contact and the stationarycontact is minimized.

Reduction of contact bounce is achieved by the relative spacing betweenstationary contacts 50 and 58, their angular relationship to each otherand their location in relationship to the path of movement of themovable ring contact 40. As movable ring contact 40 rolls into seatingengagement between stationary contacts 50-58 or 50-54 it will engage oneof the stationary contacts, it pivots about a point of contact with thefirst stationary contact and upon continued movement of rib 36, pivotsinto engagement with the second stationary contact. As pivoting occurs,a wiping action between the second engaged stationary contact andmovable contact 40 is achieved. Ring contact 40 will engage the secondstationary contact at a point about the periphery of ring contact 40 topermit nesting simultaneously with the wiping action to thereby minimizethe amount of contact bounce and provide an improved electrical contact.

FIG. 4 illustrates an embodiment of the invention wherein there is onlya pair of stationary contacts cooperating with a round movable contact.The actuation of round movable contact 60 is accomplished insubstantially the same manner as that for movable contact 40 of FIGS. 2and 3. When actuated in a predetermined direction, movable contact 60will roll along contact 62 to become nested between contacts 62 and 64and when actuated in an opposite direction, the movable contact will, asshown, become disengaged. FIG. 4 also illustrates the condition ofcontacts operating in accordance with the invention at the end of over100,000 cycles of turning 6,100 watt lights on and off. Movable contact60 has formed a slight pocket 61 in stationary contact 62 with a slightamount of mushrooming taking place at 61. In a manner similar to contact62, stationary contact 64 has been displaced at 66 to conform with thecontours of movable contact 60. Also a small amount of mushroomingmaterial 64' is noted on the top surface of the stationary contact 64.Virtually no build-up of material is realized in area 62" and 64" ofstationary contacts 62 and 64, respectively, which would provide abarrier in front of the movable contact to facilitate bouncing of themovable contact 40. As the ring contact 40 continues to move through thestationary contacts 62 and 64, continued displacement of material in thepath of the movable contact 60 will occur.

What is claimed is:

1. In an electrical switch wherein a self-centering round movablecontact engages at least three rectangular shaped stationary contacts,two of said contacts disposed in tandem relationship with a spacetherebetween, the third contact spaced from said first two contacts andoverlapping said space, said contacts further being disposed lengthwisedirectionally substantially parallel to a path of movement of saidmovable contact, and means rolling said round movable contact betweensaid stationary contacts.

2. In an electrical switch according to claim 1 wherein said stationarycontacts are skewed with respect to each other.

3. An electrical switch comprising:

three rectangular stationary contacts, each having a length, width, andthickness, two of which are dis posed lengthwise end to end with a spacetherebetween and lying in a plane substantially common to a planedetermined by the length and width of said rectangular stationarycontact, the third spaced from said first two stationary contacts andoverlapping said first named space,

a round movable electrical contact rolling on said third stationarycontact in a predetermined direction and subsequently nesting betweensaid third stationary contact and one of said first two stationarycontacts, continued cycling of said switch causing said movable contactto roll along a path and form a groove lengthwise in said one stationaryelectrical contact, and

electrical terminals electrically coupled to said stationary contacts.

4. An electrical switch comprising:

at least one pair of rectangular stationary electrical contacts disposedat an angle to each other,

a movable electrical contact ring, t

means disposed within said contact ring engaging an inner peripherythereof and providing a one-point contact therewith to roll said contactring lengthwise along one of said stationary contacts in a predetermineddirection and subsequently nesting between said stationary contacts,continued cycling of said switch causing said contact ring to roll alonga path and form a groove lengthwise in said one stationary contact, and

electrical terminals electrically coupled to said stationary contacts.

5. An electrical switch according to claim 4 wherein there are three ofsaid stationary electrical contacts two of said electrical contactsdisposed in a spaced relationship in a substantially common plane, thethird contact spaced from said first two contacts and overlapping saidfirst named space.

6. An electrical switch according to claim 4 wherein said means disposedwithin said contact ring comprises a boss and a rib carried by said bossand extending substantially across the inside diameter of said ringcontact.

1. In an electrical switch wherein a self-centering round movablecontact engages at least three rectangular shaped stationary contacts,two of said contacts disposed in tandem relationship with a spacetherebetween, the third contact spaced from said first two contacts andoverlapping said space, said contacts further being disposed lengthwisedirectionally substantially parallel to a path of movement of saidmovable contact, and means rolling said round movable contact betweensaid stationary contacts.
 2. In an electrical switch according to claim1 wherein said stationary contacts are skewed with respect to eachother.
 3. An electrical switch comprising: three rectangular stationarycontacts, each having a length, width, and thickness, two of which aredisposed lengthwise end to end with a space therebetween and lying in aplane substantially common to a plane determined by the length and widthof said rectangular stationary contact, the third spaced from said firsttwo stationary contacts and overlapping said first named space, a roundmovable electrical contact rolling on said third stationary contact in apredetermined direction and subsequently nesting between said thirdstationary contact and one of said first two stationary contacts,continued cycling of said switch causing said movable contact to rollalong a path and form a groove lengthwise in said one stationaryelectrical contact, and electrical terminals electrically coupled tosaid stationary contacts.
 4. An electrical switch comprising: at leastone pair of rectangular stationary electrical contacts disposed at anangle to each other, a movable electrical contact ring, means disposedwithin said contact ring engaging an inner periphery thereof andproviding a one-point contact therewith to roll said contact ringlengthwise along one of said stationary contacts in a pre-determineddirection and subsequently nesting between said stationary contacts,continued cycling of said switch causing said contact ring to roll alonga path and form a groove lengthwise in said one stationary contact, andelectrical terminals electrically coupled to said stationary contacts.5. An electrical switch according to claim 4 wherein there are three ofsaid stationary electrical contacts two of said electrical contactsdisposed in a spaced relationship in a substantially common plane, thethird contact spaced from said first two contacts and overlapping saidfirst named space.
 6. An electrical switch according to claim 4 whereinsaid means disposed within said contact ring comprises a boss and a ribcarried by said boss and extending substantially across the insidediameter of said ring contact.